SN75LBC784
QUADRUPLE RS-423-B DRIVER/RECEIVER
SLLS187A – NOVEMBER 1994 – REVISED AUGUST 1995
D
D
D
D
D
D
D
DW PACKAGE
(TOP VIEW)
Four Independent Drivers and Receivers
Driver Slew Rate Controlled by a Single
Resistor
Fast Driver Transition Times Down to
1.5 µs and Receiver Transition Times of
20 ns Typ
Internal Thermal-Overload Protection
RS-423-B Inputs and Outputs Designed to
Withstand ± 25 V
ESD Protection Exceeds 2000 V Per
MIL-STD-833C Method 3015
LinBICMOS Process Technology
3A
3Z
BIAS
4A
4Z
BIAS
VSS
GND
4B
4Y
3B
3Y
3C
4C
description
The SN75LBC784 performs as four independent
RS-423-B driver/receiver pairs designed to
interface data terminal equipment (DTE) with data
circuit-terminating equipment (DCE) at rates up to
120 kbps and distances to 1.2 km. The
SN75LBC784 provides an upgrade to the RS-232
serial interface and can be backward compatible
with existing serial ports while offering the higher
performance required by new faster peripherals,
such as v.34 (v.fast) modems. The RS-232
standard, and subsequent revisions, only support
data rates up to 20 kbps over about 15 meters of
cable. For RS-423-B the data rate is increased to
120 kbps and transmission distance to 1.2 km by
reducing the maximum output signal swing,
increasing the driver output current, and reducing
the receiver input voltage thresholds.
1
28
2
27
3
26
4
25
5
24
6
23
7
22
8
21
9
20
10
19
11
18
12
17
13
16
14
15
BIAS
2Z
2A
BIAS
1Z
1A
Rws
VDD
1Y
1B
2Y
2B
2C
1C
FUNCTION TABLE
A
INPUTS
B
C
L
H
L
H
L
L
H
H
H
H
L
L
L
H
L
H
L
L
H
H
OUTPUTS
Z
Y
H
H
L
H
H
L
L
L
H
?
L
L
?
L
H
?
H
L
?
H
H = high level, L = low level,
X = irrelevant, Z = high impedance (off)
? = indeterminate
The receivers consist of differential comparators with hysteresis and resistive attenuation on the inputs. The
resistive attenuation improves the input common mode range and also provides additional protection from ESD
and over-voltage stress. The differential and common mode input impedances are sufficiently high to meet
RS-423-B. When a differential voltage input of 500 mV is applied across the entire common mode range ( see
Figure 5), the receiver characteristics and bias voltage allow the receiver to remain in its intended binary state.
The drivers meet all RS-423-B specifications with built-in current limits and thermal-overload protection.
Slew-rate controlling circuitry is included in the design, which is adjusted to suit the application by means of an
external resistor (Rws). The slew rate controlling circuitry also has a default mode – if the Rws pin is shorted to
5 V externally, the transistion time defaults to approximately 1.5 ms. The BIAS input, when shorted to 5 V
externally, provides the internal node voltages. The receiver is compatible to RS-232 with the use of external
input resistors to meet the RS-232 input resistance specification of 3 kΩ to 7 kΩ.
The SN75LBC784 is characterized for operation over the temperature range of 0°C to 70°C.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
LinBiCMOS is a trademark of Texas Instruments Incorporated.
Copyright  1995, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
1
SN75LBC784
QUADRUPLE RS-423-B DRIVER/RECEIVER
SLLS187A – NOVEMBER 1994 – REVISED AUGUST 1995
logic diagram (positive logic)
3A
4A
1A
2A
1
12
4
10
23
20
26
18
3Y
3Z
4Y
4Z
1Y
1Z
2Y
2Z
2
5
27
24
11
+
_
13
9
+
_
14
19
+
_
15
17
+
_
16
3B
3C
4B
4C
1B
1C
2B
2C
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†
Positive supply voltage, VDD (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 V
Negative supply voltage, VSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 14 V
Bias voltage, Vbias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.75 V
Receiver input voltage range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 30 V to 30 V
Driver input voltage range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 0.5 V to 5.75 V
Driver output voltage range (supplies at 0 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 30 V to 30 V
Driver output voltage range (supplies at ± 12 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 25 V to 25 V
Continuous power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Dissipation Rating Table
Operating free-air temperature range, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 70°C
Storage temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C
Case temperature for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C
† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: All voltages are with respect to network ground terminal.
DISSIPATION RATING TABLE
PACKAGE
TA ≤ 25°C
POWER RATING
DERATING FACTOR†
ABOVE TA = 25°C
TA = 70°C
POWER RATING
DW
1348 mW
10.8 mW/°C
862 mW
† Derating factors are the inverse of the junction-to-ambient thermal resistance when
board-mounted with no air flow.
recommended operating conditions
MIN
NOM
MAX
UNIT
Supply voltage, VDD
10.8
12
13.2
V
Supply voltage, VSS
– 10.8
– 12
– 13.2
V
2
5
5.5
V
Bias voltage, Vbias
High-level input voltage, VIH
Driver
2
Low-level input voltage, VIL
Driver
0.8
V
High-level output current, IOH
Receiver
–4
mA
Low-level output current, IOL
Receiver
4
mA
820
kΩ
70
°C
Rws slew rate control resistor
20
Operating free-air temperature, TA
2
0
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
V
82
SN75LBC784
QUADRUPLE RS-423-B DRIVER/RECEIVER
SLLS187A – NOVEMBER 1994 – REVISED AUGUST 1995
DRIVER SECTION
electrical characteristics over recommended ranges of supply voltage and operating free-air
temperature, VDD = 10.8 V to 13.2 V, VSS = –10.8 V to –13.2 V, TA = 0°C to 70°C (unless otherwise
noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VOH
VOL
High-level output voltage
Open circuit or RL = 450 Ω
4
5.5
6
Low-level output voltage
Open circuit or RL = 450 Ω
–6
– 5.5
–4
V
IIH
IIL
High-level input current
VI = 2.4 V to 5.5 V
VI = 0 V to 0.8 V
100
µA
IO
IOS(H)
Output leakage current
IOS(L)
Low-level short circuit output current
Low-level input current
High-level short circuit output current
IDD
Supply current
ISS
Supply current
Ibias
Bias current
µA
– 100
VDD = VSS = 0,
VI = 5 V,
VO = ± 6 V
VO = 0
VI = 0,
No load
VO = 0
V
100
µA
15
45
mA
– 45
– 15
mA
– 100
10
12
60
70
No load
– 10
– 12
RL = 450 Ω
– 60
– 70
RL = 450 Ω
400
mA
mA
µA
switching characteristics over recommended ranges of supply voltage and operating free-air
temperature, VDD = 10.8 V to 13.2 V, VSS = –10.8 V to –13.2 V, TA = 0°C to 70°C (unless otherwise
noted)
PARAMETER
TEST CONDITIONS
MIN
Rws = 0 kΩ
tTLH
Transition time, low-to-high level (see Figure 1)
CL = 50 pF,
MAX
UNIT
1.5
Rws = 20 kΩ
1.5
2.1
2.7
Rws = 82 kΩ
5
8
11
Rws = 820 kΩ
RL = 450 Ω,
VWS = 5 V
TYP
µs
80
1.5
Rws = 0 kΩ
Rws = 20 kΩ
1.5
2.1
2.7
Rws = 82 kΩ
5
8
11
µs
tTHL
Transition time, high-to-low level (see Figure 1)
SR
Output slew rate
Rws = 20 kΩ
15
V/µs
tsk
Output skew (see Figure 4) |tPHL – tPLH|
Rws = 82 kΩ
1
µs
Rws = 820 kΩ
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
80
3
SN75LBC784
QUADRUPLE RS-423-B DRIVER/RECEIVER
SLLS187A – NOVEMBER 1994 – REVISED AUGUST 1995
RECEIVER SECTION
electrical characteristics over recommended ranges of supply voltage and operating free-air
temperature, VDD = 10.8 V to 13.2 V, VSS = –10.8 V to –13.2 V, TA = 0°C to 70°C (unless otherwise
noted)
PARAMETER
VIT
IT+
Positive input threshold voltage
VIT
IT–
Negative input threshold voltage
II
Input current
Vhys
Hysteresis (VIT + – VIT –)
TEST CONDITIONS
MIN
TYP
MAX
200
With 500 Ω series resistor
400
– 200
With 500 Ω series resistor
VI = 10 V
VI = – 10 V
– 400
Other input to GND
1.3
– 3.25
– 1.3
20
40
VOH
High level output voltage (see Note 2)
High-level
IO = –20 µA
IO = – 4 mA
VOL
IRX
Low-level output voltage
IO = 20 µA to 4 mA
VID
Vofs
Differential input voltage
Receiver inputs open circuit
1.6
Fail safe output voltage
See Note 3
3.5
3.25
150
3.5
5
2.4
5
RX short circuit current
2.1
UNIT
mV
mV
mA
mV
V
0.4
V
50
mA
2.6
V
V
NOTES: 2. Device has an internal RX supply regulator. Maximum RX logic output voltage under no load is thus defined by an internal voltage
value. This is nominally set to 4.5 V with a tolerance of ± 5%.
3. One input at ground, other input open circuit, IO = –20 µA, or both open circuit.
switching characteristics over recommended ranges of supply voltage and operating free-air
temperature (unless otherwise noted)
test conditions: VDD = 10.8 V to 13.2 V, VSS = – 10.8 V to – 13.2 V, TA = 0°C to 70°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
tPLH
tPHL
Propagation Delay time low-to-high (see Figure 2)
tTHL
tTLH
Transition time high-to-low (see Figure 3)
4
Propagation delay time high-to-low (see Figure 2)
NOM
MAX
UNIT
0 15
0.15
1
µs
20
200
ns
CL = 50 pF
Transition time low-to-high (see Figure 3)
POST OFFICE BOX 655303
MIN
• DALLAS, TEXAS 75265
SN75LBC784
QUADRUPLE RS-423-B DRIVER/RECEIVER
SLLS187A – NOVEMBER 1994 – REVISED AUGUST 1995
PARAMETER MEASUREMENT INFORMATION
5V
Rws
3V
Input
(see Note A and B)
VDD
0V
Input
Output
51 Ω
VSS
GND
RL
VOH
90%
Output
CL
90%
10% 10%
VOL
tTHL
tTLH
GND
Figure 1. Driver Transition Times
Input
+
51 Ω
0.5 V
Input
(see Note A and C)
VDD
50%
50%
– 0.5 V
tPHL
tPLH
Output
–
CL
50%
Output
50%
VSS
GND
GND
Figure 2. Receiver Propagation Delay Times
0.5 V
Input
(see Note A and C)
VDD
– 0.5 V
Input
+
51 Ω
GND
Output
–
CL
VOH
Output
VOL
90% 90%
10% 10%
tTLH
VSS
tTHL
GND
Figure 3. Receiver Transition Times
NOTES: A. CL includes probe and jig capacitance.
B. The input pulse is supplied by a generator having the following characteristics: tr ≤ 10 nS, tf < 10 nS, Zo = 50 Ω, PRR ≥ 5 kHz, duty
cycle 50%, Vmax = 3 V, Vmin = 0 V.
C. The input pulse is supplied by a generator having the following characteristics: tr ≤ 10 nS, tf < 10 nS, Zo = 50 Ω, PRR ≥ 5 kHz, duty
cycle 50%, Vmax = 0.5 V, Vmin = – 0.5 V.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
5
SN75LBC784
QUADRUPLE RS-423-B DRIVER/RECEIVER
SLLS187A – NOVEMBER 1994 – REVISED AUGUST 1995
PARAMETER MEASUREMENT INFORMATION
50%
Input A
50%
tPLH
Output Y
tPHL
50%
50%
Figure 4. Skew Definition Times
500 Ω
250 mW
250 mW
500 Ω
Vcm
Vcm = – 7 to 7 V
Figure 5. Receiver Input Balance Test
6
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
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Copyright  1998, Texas Instruments Incorporated